Transverse Flow Marine Turbine with Autonomous Stages

ABSTRACT

The invention relates to a turbine engine including a stack of stages, each of which includes a cross-flow turbine and a generator, where each turbine-generator stage has an independent shaft, and wherein each stage is associated with an independent fairing ( 31 - 32 ) directing it with respect to a current, each fairing being of shroud type, with symmetrical profiled wings.

BACKGROUND

The present invention relates to transverse flow hydraulic turbineengines formed of at least one column of stacked turbines.

DISCUSSION OF THE RELATED ART

The applicant has filed a set of patent applications relative tocross-flow hydraulic turbine engines, among which:

-   -   French patent application 04/50209 filed on Feb. 4, 2004 (B6412)        relative to a cross-flow hydraulic turbine engine comprising a        column of turbines, each turbine comprising blades in the form        of V-shaped wings;    -   French patent application 05/50420 filed on Feb. 14, 2005        (B6869) relative to a holding structure intended to stiffen a        turbine column and to avoid its deformation; and    -   patent application PCT/FR2008/051917 filed on Oct. 23, 2008        (B8450) relative to a turbine engine formed of an assembly of        two twin columns turning in opposite directions.

These patent applications, which will be considered as known herein,describe turbine engines formed of at least one column of stackedturbines rigidly attached to a common shaft. This common shaft transmitsa rotating force to a single generator associated with each column.

Patent applications 05/50420 and PCT/FR2008/051917 provide using afairing formed of two hollow profiled walls, or wings, intended toconcentrate the incident flow towards the turbines and thus increasetheir efficiency. In all the described cases, the fairing is one-piece,that is, a single fairing is associated with all the turbines of acolumn or a pair of columns. As known, the association of such a fairingwith a turbine, when the walls are wing-shaped, enables, when thisfairing is maintained symmetrical facing the current, to substantiallymultiply by two the efficiency if the chord of each wing has a lengthsubstantially equal to three times the turbine diameter.

The intensity of a sea or river current is capable of varying alongtime. Now, the maximum power delivered by a turbine is obtained for aspeed of rotation of the drive blades which depends on the velocity ofthe current which reaches it. A speed variation system for controllingalong time the rotation speed of the drive shaft, identical to therotation speed of each of the turbines of a column, has thus beenprovided. The speed variation system may be formed from a measurement ofthe upstream velocity of the sea or river current which reaches thecolumn or directly from an analysis of the power provided by the column.

Apart from having a variable intensity, the current may vary along timein terms of orientation. Such variations are observed in periodicallyreversing tidal currents, that is, unidirectional tides, as well as intidal currents rotating under the effect of the Coriolis force fordepths greater than approximately 10 meters. In patent applications05/50420 and PCT/FR2008/051917, various means have been provided toforce the orientation of such turbine engines, at any time and globally,according to the orientation of the current: motor assistance, orautorotation by use of vane-type tail units. The autorotation may alsobe ensured by placing the rotation axis of the turbine engine upstreamof the two resultant forces which exert on each of the hollow profiledwalls and which cross their respective thrust centers.

Except for a possible draught, the entire height of the current all theway down to the sea or river ground may be exploited by a turbinecolumn. The latter thus face intensity variations which inevitablyappear in the lower portion. In French patent application 05/50420,relative to the current intensity variation according to depth, it hasbeen provided to arrange, between the hub of each turbine and theassociated drive shaft portion, a gear box or any other system enablingto control the rotation speed of the drive blades. The arranging of sucha system at the level of each turbine enables to operate each turbine ofa column so that it provides a maximum power for a given orientation ofthe current. However, apart from its intensity variations, a current mayvary according to depth and also in terms of orientation in sea caseswhere large-scale flow systems generate winds capable of influencingtidal currents. Now, in the disclosed system, fairings form a blockassociated with an entire column and it is accordingly impossible toenvisage optimally adapting the fairing direction for each turbine.Finally, this system is modular neither in its structure, nor in itsoperation since the blocking of a turbine results in the blocking of thecolumn.

Patent application DE-A-10065548 provides, in the field of windturbines, a single-column turbine engine in which each stage comprises aturbine and a generator assembled on a shaft independent from that ofthe other stages. The installing of a system enabling to control theblade rotation speed of each turbine enables to operate each turbineoptimally in terms of efficiency but also of hold of the assembly sincetwo successive stages are capable of rotating in opposite directions. Itwill be underlined that this patent application relates to wind turbinesand that no fairing is provided therein.

All these turbine engines have one or other of various disadvantages anddo not provide an optimal efficiency.

SUMMARY

An object of embodiments of the present invention is to provide across-flow turbine engine structure with turbine columns cumulating theadvantages, in theory incompatible, of various previous structures, tooptimize the efficiency.

Another object of embodiments of the present invention is to provide aturbine engine which is particularly simple to form, to maintain, toassemble, and to disassemble.

Another object of embodiments of the present invention is to provide aturbine engine where the blocking of a turbine does not block an entirecolumn.

Another object of embodiments of the present invention is to provide aturbine engine where each turbine may rotate at a speed optimallyadapted at any time to the effective intensity of the current velocityat the turbine level.

Another object of embodiments of the present invention is to provide aturbine engine where each turbine may rotate at a speed optimallyadapted at any time to the effective orientation of the current at theturbine level.

Another object of embodiments of the present invention is to provide aturbine engine having a height modularity, that is, a number of stackedturbine stages, which has no influence on the selection of thegenerators, thus providing a greater manufacturing modularity.

To achieve these and other objects, an embodiment of the presentinvention provides a turbine engine comprising a stack of stages, eachof which comprises a cross-flow turbine and a generator, where eachturbine-generator stage has an independent shaft, and wherein each stageis associated with an independent fairing directing it with respect to acurrent, each fairing being of shroud type, with symmetrical profiledwings.

According to an embodiment of the present invention, the generators ofthe various stages are interconnected via rectifiers.

According to an embodiment of the present invention, the output of eachrectifier is coupled to independent charge means for controlling therotation speed of the associated generator or blocking it.

According to an embodiment of the present invention, two adjacent stagesare designed so that their turbines rotate in opposite directions.

According to an embodiment of the present invention, each stage iscoupled to the neighboring stages by controlled means setting the mutualorientation of the stages.

According to an embodiment of the present invention, eachturbine-generator-fairing stage forms an independent module stackable insitu on another module.

According to an embodiment of the present invention, each modulecomprises a frame comprising the two walls of a shroud-type fairing,associated with an upper plate and a lower plate; a first housingattached to the lower plate and containing the generator; and a thirdplate rotatably assembled with respect to the lower plate, under thehousing, this third plate being provided with means of attachment to alower module.

According to an embodiment of the present invention, the attachmentmeans comprise pins insertable into a lower module.

According to an embodiment of the present invention, each stagecomprises a couple of contra-rotating turbines, each turbine beingassociated with a generator contained in a housing, each turbine beingseparated from the other by a symmetrical profile extending downstreamat least all the way to the trailing edge, each stage being separatedfrom the neighboring stages by an upper plate and a lower plateextending from the profile all the way to the fairings.

According to an embodiment of the present invention, the blades of eachturbine are of V-shaped wing type.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages will bediscussed in detail in the following non-limiting description ofspecific embodiments in connection with the accompanying drawings, amongwhich:

FIG. 1A is a perspective view of an example of single-column turbineengine;

FIG. 1B is a perspective view of a stage of the turbine engine of FIG.1A;

FIG. 1C is an axial cross-section view of a stage of the turbine engineof

FIG. 1A;

FIG. 2A is a perspective view of an example of single-column turbineengine;

FIG. 2B is a simplified top view, in cross-section, of a turbine of FIG.2A;

FIG. 2C is a cross-section view of an embodiment of a stage of theturbine engine of FIG. 2A;

FIG. 2D is a cross-section view of another embodiment of a stage of theturbine engine of FIG. 2A;

FIG. 3A is a perspective view of an example of a turbine engine withtwin columns;

FIG. 3B is a perspective view of a stage of the turbine engine of FIG.3A; and

FIG. 4 is a perspective view of an example of a turbine engine with twincolumns.

DETAILED DESCRIPTION

FIGS. 1A, 1B, and 1C are simplified views respectively showing asingle-column cross-flow hydraulic turbine engine, a perspective view ofa stage of this turbine engine, and a partial cross-section view of astage of this turbine engine. These views are simplified in that,especially, they do not show the means for attaching or connecting theturbine engine. Turbine engine 1 is formed of an assembly of stages 3where each stage comprises a cross-flow turbine 5 and a generator 7.Each elementary turbine for example is of the type described in patentapplication 04/50209 (B6412) and is rigidly attached to a shaft 8rotatably assembled between upper and lower flanges 9 and 10 connectedby posts 11. The shafts of the various turbine-generator stages areindependent from one another. Each shaft 8 drives rotor 12 of agenerator 7, the rotor rotating inside of a stator 13 which provides anelectric power supply via conductors 14.

Conductors 14 of the various generators are interconnected, directly inparallel or by any other connection means capable of providing anelectric power supply when the turbines of the turbine engine arerotated. It may be provided to associate a rectifier with the output ofeach generator to allow specific independent controls of each of thegenerators in terms of torque and/or of rotation speed. The differentrectifiers are then connected in parallel on a D.C. bus. For theconnection to the network, a single inverter is necessary, placed afterthe D.C. bus.

Further, the adjacent turbines of a same column are preferably designedto rotate in opposite directions when a sea or river current acts on thecolumn. For example, in the embodiment of FIG. 1A, blades 21, 22, 23, 24of the adjacent turbines are oriented differently so that the turbinescomprising blades 21 and 23 rotate in a first direction and that theturbines comprising blades 22 and 24 rotate in the opposite direction.As a result, when the column is submitted to the action of a hydrauliccurrent, it is only submitted to a drag force which tends to give it aflexion in the current direction. Given the opposite rotation of twoadjacent turbines of the column, the lift forces orthogonal to thedirection of the current mutually cancel or are at least stronglydecreased. The lateral load tipping moment resulting from the sum of themoments associated with the lift forces of each turbine is furtherdecreased.

FIGS. 2A and 2B respectively are a perspective view of an example of asingle-column cross-flow turbine engine and a simplified top view of aturbine and of its associated fairing.

The turbine engine comprises the same elements as FIGS. 1A to 1C, whichwill not be described again. Further, each stage forms a self-containedmodule comprising a turbine, a generator, and a frame. This framecomprises a fairing formed of two vertical or symmetrical shaped walls(or wings) 31, 32, an upper plate 41, and a lower plate, not shown inFIG. 2A. A lower fairing element 33 protects the generator. Protectionelements 34 are intended to avoid any shock between the turbine bladesand possible bodies driven by the current which actuates the turbine.The turbine engine is assembled in a way not shown on a foundationstructure so that the lower stage can freely rotate around a verticalaxis.

The top view of FIG. 2B schematically shows three blades 21A, 21B, and21C of a turbine and two profiled wings 31, 32 of the associatedfairing. Direction A corresponds to the axis of symmetry of the moduleand arrow C indicates the current direction. Each wing 31, 32 has achord with an inclination relative to the axis of symmetry defined by anangle β. Angle β ranges between a value of the incidence close tocritical incidence α_(c) (detachment), that is, substantially between10° and 25° and an inclination of one third thereof. The detachment hereis considered in the presence of turbine in the shroud, and may bedifferent from the detachment for an isolated profile or a couple ofopposite profiles. As indicated, the association of such a fairing,independent at each stage, gives the possibility of optimizing thesystem operation.

Thus, calling β-kβ the angle between the direction of the current andthe axis of symmetry of the system, and if the turbine rotates in thedirection indicated by arrow R, angle α_(r) between the chord of thewing going up with the current and direction C of the current is equalto kβ and angle α_(d) between the chord of the wing going down with thecurrent and direction C of the current is equal to (2−k)β. The optimaldirection of the fairing is that where the profiled wall correspondingto the blade motion against the current has an incidence α_(r) smaller β(corresponding to a fraction k β of β, value k depending on the selectedprofile, on the incident velocity of the current, and on the rotationspeed of the machine). In such an orientation, each blade is confrontedto an overspeed (or even an underspeed if k<0 with respect to theincident velocity) which is lower when it moves against the current thanif aα_(r)=β. On the other hand, the profiled wall corresponding to thedescending motion of the blades must have an incidence α_(d)=(2−k)βgreater than β, close to, but smaller than α_(c). The overspeed isaccordingly greater during the descending motion than if α_(d)=β. In theprior art case of a tower (a column of stages) comprising a one-piecefairing plunged in a flow with non-uniform directions, some stages,however, will have a strong efficiency drop (which may reach 50%) ifincidence α_(r) is stronger than β by from 5 to 10 degrees.

The natural (passive) orientation of the fairing of an independentmodule is close to a symmetrical situation, facing the current,α_(r)#α_(d) <β for ordinary values of the advance ratio (between 2 and5), which is the ratio of the speed of a blade tip to the currentvelocity. This natural orientation provides an efficiency close, tobetter than within 20%, to the efficiency corresponding to an optimalorientation. The optimal efficiency of the turbine is thus approached,which shows the advantage of freely rotating independent stages. It iseventually advantageous, in this case, for β to be close to α_(c): themore the shroud is open, the greater the acceleration of the fluidtherein (only limited by cavitation) and the higher the sampled power.

According to a variation of the present invention, instead of providingstages freely rotating with respect to one another, it may be providedto bind each stage to an adjacent stage by a motor-driven systemenabling to impose or to adjust the angular shift between two stages.Thus, the passive orientation situation may be advantageously modifiedby a forced orientation which corresponds, at any time and for eachstage, to the optimal orientation. Such a control then combines withthat of the turbine rotation speed.

The use of turbine-generator-fairing stages is particularly advantageousand, in addition to efficiency gains, provides several advantages,including the following points.

-   Each fairing wing may be lightened with respect to prior systems    where a large wing has to withstand the stress of the structure.-   It becomes possible to smooth along time the stress on the holding    structures in a change of tide, the stages rotating with respect to    one another with a given angular shift, which avoids repositioning    jolts. The structure for holding a column formed by the coupling of    the stacked frames can then be lighter. Indeed, it only has to    resist flexural stress in a given direction and not additional    variable stress orthogonal to this direction.-   The adjacent turbines of a same column may be designed to rotate in    opposite directions when a sea or river current acts on the column.    Given the opposite rotation of two adjacent turbines of the column,    the lift forces orthogonal to the direction of the current which are    exerted on the coupled frames mutually cancel or are at least    strongly decreased.

FIG. 2C is a cross-section view illustrating an example of aturbine-generator-frame stage usable in the structure of FIG. 2A. Thisstructure does not exactly correspond to the cross-section view of FIG.2A, but illustrates certain variations which will clearly occur to thoseskilled in the art.

The two wings 31, 32 of the fairing are connected by an upper plate 41.This plate comprises openings 42, 43 intended to receive screws 44 ofassembly to a neighboring stage. The two wings are also connected by alower plate 45. Shaft 8 of turbine 5 is pivotally assembled on bearings47, 48 respectively fixedly attached to upper plate 41 and to lowerplate 45. Shaft 8 is connected to rotor 50 of a generator arranged onthe side of plate 45 opposite to the turbine. Stator 52 of the generatoris attached, for example, via a housing 53, to plate 45. A second plate60 is assembled to freely rotate in a plane parallel to that of plate45. The articulation between plate 60 and plate 45 is as an exampleformed of two circular bearings 62, 63 respectively assembled on thebottom of plate 45 and on the lateral wall of housing 53.

Of course, various alternative embodiments are possible, the importantpoint being to have a freedom of rotation between the fairing of a stageand the underlying stage.

FIG. 2D is a cross-section view illustrating another example of aturbine-generator-fairing stage usable in the structure illustrated inFIG. 2A. While the structure of FIG. 2C is intended to be assembledbefore immersion (due to the presence of screws or bolts 44), thestructure of FIG. 2C is intended to be assembled in situ, stage bystage. FIG. 2D shows the same elements as in FIG. 2C designated with thesame reference numerals. As concerns the assembly mode, openings 42, 43and assembly screws 44 are replaced with openings 71, 72 and pins 73,74. Thus, the structure may be assembled in situ, stage by stage.

Among the advantages of the embodiments of FIGS. 2C and 2D, theexistence of plates separating two adjacent stages should be noted. Thisavoids for turbulent flows created by the rotation of elements of astage to propagate to an adjacent stage.

FIGS. 3A and 3B are perspective views of a turbine engine with twincolumns and of a stage of such a turbine engine. For the design of sucha structure and the forming of different variations, reference may bemade to above-mentioned patent application PCT/FR2008/051917. In theshown example, the various elements of the fairing are fixed withrespect to one another and the assembly is rotatably mobile around apile 80 which is for example rotatably assembled on a fixed base.

In this embodiment, the elements of a column rotate in a directionopposite to that of the elements of the adjacent columns to suppresslift forces on the entire structure. Each stage comprises a pair ofturbines 41, 42, associated with a pair of generators 43, 44.

FIG. 4 shows a turbine engine with several turbine-generator-fairingstages with twin columns forming an advantageous modification of thestructure of FIG. 3A. The fairing of each of the stages is independentfrom the fairing of the other stages. Each stage is articulated withrespect to the upper stage by means of a pile (not shown) which crossesall stages at the level of the median wall and which is attached to afoundation. The pile blocks radial and axial displacements. The freedomof rotation is provided between stages by thrust bearings around thepile.

FIG. 4 shows an example where the orientation of the current variesbetween the bottom and the upper portion of the structure. The currenthas been assumed to vary regularly. Accordingly, each of the stages isangularly shifted in the same direction with respect to the previousstage. For such a turbine engine with several twin-columnturbine-generator-fairing stages, and unlike a single-column turbineengine:

-   the natural (passive) orientation of the fairing is exactly the    symmetrical situation “facing the current”,-   the optimal orientation of the fairing is exactly the natural    orientation of the fairing.

Stages each comprising a turbine, a generator, and a fairing have beendescribed, where these stages can be stacked and assembled in variousmanners. Specific embodiments of turbines, of generators, and offairings have been described. It will be understood by those skilled inthe art that the forming of each of these elements is likely to havemany alterations, examples of which can especially be found in priorpatents applications of the applicant, without this being a limitation.

The above-described turbine-generator-fairing stage stack structurescombine the following features and advantages.

-   1. Ease of assembly/disassembly: each turbine stage can be easily    stacked by engaging on another stage. Further, the    turbine-generator-fairing stages described herein enable to form a    turbine engine which is easy to disassemble and to transport, each    stage thereof having an equivalent weight which, in practical    implementations, will not exceed a value ranging between 2 and 5    tons.-   2. Electric autonomy both in terms of electric conversion (one    generator per turbine) and of driving of the rotation speed    according to the value of the incident velocity at the considered    stage, to obtain the optimal efficiency (one control system per    stage). Such an independence enables to reflect an inhomogeneity in    terms of altitude of the intensity of the speed. As a result of this    autonomy, it is possible, if necessary, for example in the    occurrence where a turbine should fail, to slow down, for example,    by electrically overcharging it, the generator of an adjacent or    neighboring turbine. It is finally possible to adapt the number of    stages according to the implantation site without modifying the    generator.-   3. Mechanical autonomy: in the case where a turbine is blocked, the    other turbines of the same column remain active, possibly by taking    the precaution mentioned at point 2 hereabove.-   4. Hydrodynamic operation independence: there is no interaction    between two stacked turbines, between a turbine and its shaft,    between a generator and a turbine etc., which would adversely affect    the performance of each stage, due to the plates separating    neighboring stages.-   5. Dynamic stability of the assembly of stages against vibrations    induced by lift forces, and the resonance phenomena that may result    therefrom, due to the inversion of the rotation direction between    stages of a column, in the case of a single-column machine.-   6. Static stability of the assembly of stages against drag forces    which tend to flex the column in the current direction, or even to    drag away the turbine engine along the current. The tipping moments    induced by such forces are much greater than those of the lift    forces; they may be difficult to balance when criteria 1), 3), and    the following criterion 7) are desired to be introduced.-   7. Optimization of the stage orientation: significant performance    gains (at least doubled) are achieved by the use of shrouds, if    these shrouds result in an optimal orientation of each stage with    respect to the current direction.

The present invention is likely to have various alterations andmodifications which will occur to those skilled in the art, who mayespecially adapt various alterations described in prior publications ofthe inventors.

The case where two adjacent turbines of a turbine engine rotate inopposite directions has been described. Different groups of turbinesrotating in opposite directions may also be provided.

Finally, the present invention has been described in the case of turbineengines operating in liquid currents (hydraulic turbine engines). Thepresent invention may be adapted to turbine engines operating in gascurrents (wind turbine engines).

1. A turbine engine comprising a stack of stages, each of whichcomprises a cross-flow turbine and a generator, wherein eachturbine-generator stage has an independent shaft-ft and wherein eachstage is associated with an independent fairing directing it withrespect to a current, each fairing being of shroud type, withsymmetrical profiled wings.
 2. The turbine engine of claim 1, whereinthe generators of the various stages are interconnected via rectifiers.3. The turbine engine of claim 2, wherein the output of each rectifieris coupled to independent charge means for controlling the rotationspeed of the associated generator or blocking it.
 4. The turbine engineof claim 1, wherein two adjacent stages are designed so that theirturbines rotate in opposite directions.
 5. The turbine engine of claim1, wherein each stage is coupled to the neighboring stages by controlledmeans setting the mutual orientation of the stages.
 6. The turbineengine of claim 1, wherein each turbine-generator-fairing stage forms anindependent module stackable in situ on another module.
 7. The turbineengine of claim 1, wherein each module comprises: a frame comprising thetwo walls of a shroud-type fairing, associated with an upper plate and alower plate, a first housing attached to the lower plate and containingthe generator, and a third plate rotatably assembled with respect to thelower plate, under the housing, this third plate being provided withmeans of attachment to a lower module.
 8. The turbine engine of claim 7,wherein the attachment means comprise pins insertable into a lowermodule.
 9. The turbine engine of claim 1, wherein each stage comprises acouple of contra-rotating turbines, each turbine being associated with agenerator contained in a housing, each turbine being separated from theother by a symmetrical profile extending downstream at least all the wayto the trailing edge, each stage being separated from the neighboringstages by an upper plate and a lower plate extending from the profileall the way to the fairings.
 10. The turbine engine of claim 1, whereinthe blades of each turbine are of V-shaped wing type.